I think this is beginning to look like a scam. Gay couple could be out shopping bakeries until one refuses to make the cake. Wahh, they call discrimination. Meantime, there are plenty of gay-friendly bakeries who would have gladly taken the job. The targeted bakery should have checked to see how many bakeries these folks went to before finding one who refused. I'd have paid a PI to have that done or done it myself.
This all reminds me of the lawyers and activists who go around looking for mom and pop operations to sue over ADA accommodations, even if only slightly not up to speed.